Papers by Keyword: Melt Treatment

Abstract: The article is devoted to studying the effect of liquid melt treatment with a substance having high affinity with hydrogen – lead-base silumin. Taking into account that gases (hydrogen, nitrogen and oxygen) are present everywhere, including alloys, a series of experiments was carried out on treating melt of blast furnace iron with substances having great affinity with hydrogen. It is established: when treating melt with lead-base silumin in the low-temperature test interval, there is a slight increase in the linear expansion coefficient (LEC) at 100°C, compared with the initial one, to 8.210^-6, deg^-1. In the temperature range of 100-150°C LEC decreases to a minimum value of 7.210^-6, deg^-1. In the average temperature range of 150-300°C, a sharp, anomalous increase is noticeable, compared with the initial one up to 15.5210^-6, deg^-1. When studying the microstructure of cast iron after processing the melt with lead silumin, the formation of ledeburite structure is stated. Samples treated with lead-base silumin were subjected to cementation by feeding water steam at 900°C for 1-5 hours. It should be noted that, in the temperature range of 50-150°C, the values of the linear expansion coefficient lie almost in a straight line in the entire field of study. The coefficient varies from 10.810^-6, deg^-1 at 50°C to 13.710^-6, deg^-1 at 450°C. Preliminary heat treatment of cast iron in the carburizer made by the Bondyuzhsky plant with water steam smoothes anomalies of LEC and increases its initial values, and grinds perlite and cementite as well. Subsequent quenching in water with a temperature of 1000°C significantly changes the linear expansion coefficient of cast iron. Hardening of samples after cementation sharply reduces the linear expansion coefficient in the test range of 150-200°C, and in the temperature range of 350-450°C negative values of LEC are observed. Thus, it can be concluded, that treating the melt with lead-base silumin, cementation in the medium of the carburizer made by the Bondyuzhsky plant and subsequent hardening leads to sharp changes of the linear expansion coefficient up to negative values. The identified properties suggest the possibility of using cast iron where it is necessary to constancy of LEC and there are no requirements for the weight of the product.

Abstract: The microstructure and mechanical properties of 7050 alloy rheo-castings after treated by Annular Electromagnetic Stirring (A-EMS) melt treatment were investigated. The results revealed that, under A-EMS, the refinement and homogeneity of the solidification structure could be improved greatly and the slurry was suitable for the following rheo-casting; and also the hot-cracking defects in the casting process were significantly alleviated, meanwhile, the strength and ductility of the alloy casting were found to be comparable to those of conventionally forged 7000 series alloys.

Abstract: The resource-saving technology for producing of thin-walled castings from A356.1, A413.1 and A360.0 aluminum alloys by the lost foam casting method, as well as the results of this technology implementation in production conditions are considered in the paper. The technology involves thermo-speed treatment of the melt with the predominance of secondary materials in charge (85...90 wt.%), including isothermal holding and subsequent rapid cooling of the melt for fixation the high-temperature state. It is shown that the use of thermo-speed treatment promotes the production of aluminum castings with fine-grained microstructure and the enhanced level of mechanical properties without the addition of costly modifying additives, and makes it possible to use an increased amount of secondary charge materials during smelting.

Abstract: Al-Si alloys were characterized by excellent corrosion and wear resistance, low thermal expansion and high specific strength. Adding Ni to Al-Si alloy contributes to enhance the elevated temperature strength. However, the coarse structures and Ni-containing phases are disadvantageous for the mechanical properties. In this paper, an advanced melt treatment technology named the annular electromagnetic stirring (A-EMS) process was utilized for the Al-10Si-1.1Ni alloy to examine the effects of A-EMS on structures and mechanical properties. Research results showed that in the case of A-EMS, the billets with finer solidification structures and Ni-containing phases morphology as well as higher performance were achieved.

Abstract: Electromagnetic stirring (EMS) process, as an advanced melt treatment technology, is increasingly applied in metallurgy industry. Direct chill (DC) casting process by annular electromagnetic stirring (A-EMS) was applied in this study to investigate the solidification behavior of a modified 7N01 alloy, and the effects of DC casting process without EMS, and A-EMS casting process on microstructure, composition segregation and mechanical properties of continuously cast billets were compared. The research results showed that the billets with higher performance, lower macro-segregation, more uniformly fine solidification structure were obtained in case of A-EMS.

Abstract: A novel process for grain refining and manufacture of high quality semisolid slurries ofalloys was developed. The process was proven to refine metal grain remarkably, and the grain sizeof pure aluminum can be refined to the first grade of Chinese refining standard of pure aluminumGB/T 7946.4-1999 ref) . P rimary silicon and eutectic silicon in the hypereutectic Al-Si alloy can bealso effectively refined. This process was used to prepare the billets with small spherical grains orequiaxed grains of Al-6Si-2Mg, AZ91, AZ31 and hypereutectic Al-Si alloys successfully. The p ip es ,profi le s and wire s of 6201, AZ31 and AZ61 alloys were produced by continuous rheo-extrusion.The strips of AZ91, AZ31, and Mg-Sn alloys were prepared by rheo-rolling. As an innovativeprocessing technology with low cost and high efficiency, vibrating sloping plate melt treatment hasgood prospective application in many fields such as rheo-casting, rheo-extrusion, rheo-rolling,metal microstructure refinement, etc.

Abstract: An advanced rheo-squeeze casting process, based on the annular electromagnetic stirring (A-EMS) melt treatment technology was developed by GRINM for manufacturing near-net shape Al-alloy components with high integrity. Effects of A-EMS melt treatment process on microstructure and property of squeeze casting Al-Zn-Mg-Cu-Sc alloys were studied. The results revealed that the A-EMS melt treatment process apparently benefited grain refinement and homogeneity, and the hot-cracking of the test alloy for a complicated casting was significantly alleviated, and thus the strength and ductility of the casting were found to be comparable to those of conventionally forged alloys.

Abstract: The annular electromagnetic stirring (A-EMS) process, as an advanced melt treatment technology, is increasingly applied in metallurgy industry. DC casting by A-EMS was applied in this study to investigate the solidification behaviour of a modified 7075 alloy. The effects of DC casting without EMS, with normal electromagnetic stirring (N-EMS) and with annular electromagnetic stirring (A-EMS) on microstructure, composition segregation and mechanical properties of continuously cast billets were compared. Research results showed that the billets with higher performance, lower macro-segregation, more uniformly fine solidification structure were obtained in the case of A-EMS.

Abstract: Ultrasonic processing is known to be an efficient means of aluminium melt degassing and structure modification with additional benefits of being economical and environment friendly. This paper reports on the kinetics of ultrasonic degassing effect of foundry alloys. Direct measurements of hydrogen concentration in the melt by Foseco Alspek-H probe are used along with the reduced-pressure test. The effects of ultrasonic processing on structure, i.e. grain size and porosity, are studied using metallography and 3D X-ray tomography. This work is performed within the Ultragassing project funded by the European Union’s 7^th Framework Program.

Abstract: The influences of different preheating temperature of mold and treatment temperature on solidified structure of LC9 alloy were studied by low-power ultrasonic vibration melt-treatment. The results show that grain of LC9 alloy can be refined greatly by low-power ultrasonic vibration melt-treatment. The dendrite growth is restrained and the microstructure is changed from larger dendrite grains to dominant fine none-dendritic and globular grains. With the decrease of preheating temperature of mold, grain size decreases. The efficiency of grain refinement is better at low preheating temperature. With the increase of ultrasonic vibration temperature, grain size decreases firstly, then increases, and the turning point is 660 °C. At 640 °C, grain size of the alloy with US vibration treatment changes slightly compared with non US-treated alloy.